The present disclosure relates to vision correcting systems and more specifically to vision correcting computational light field image display systems and methods. The various embodiments enable a vision correcting display that compensates for aberrations using inverse blurring and a light field display.
Today, millions of people worldwide suffer from myopia. Eyeglasses have been the primary tool to correct such aberrations since the 13th century. Recent decades have seen contact lenses and refractive surgery supplement available options to correct for refractive errors. Unfortunately, all of these approaches are intrusive in that the observer either has to use eyewear or undergo surgery, which can be uncomfortable.
Since their introduction to computer graphics, light fields have become one of the fundamental tools in computational photography. Frequency analyses for instance, help better understand the theoretical foundations of ray-based light transport whereas applications range from novel camera designs and aberration correction in light field cameras, to low-cost devices that allow for diagnosis of refractive errors or cataracts in the human eye. These applications are examples of computational ophthalmology, where interactive techniques are combined with computational photography and display for medical applications.
Glasses-free 3D or light field displays were invented in the beginning of the 20th century. The two dominating technologies are lenslet arrays and parallax barriers. Today, a much wider range of different 3D display technologies are available, including volumetric displays, multifocal displays, and super-multi-view displays. Volumetric displays create the illusion of a virtual 3D object floating inside the physical device enclosure; the lens in the eye of an observer can accommodate within this volume. Multifocal displays enable the display of imagery on different focal planes but require either multiple devices in a large form factor or varifocal glasses to be worn. Super-multi-view displays emit light fields with an extremely high angular resolution, which is achieved by employing many spatial light modulators. Most recently, near-eye light field displays and compressive light field displays have been introduced. With one exception (MAIMONE, A., WETZSTEIN, G., HIRSCH, M., L A:—IMAN, D., RASKAR, R., AND FUCHS, H. 2013. Focus 3d: Compressive accommodation display. ACM Trans, Graph. 32, 5, 153:1-153:13.), none of these technologies is demonstrated to support accommodation.
Building light field displays that support all depth cues, including binocular disparity, motion parallax, and lens accommodation, in a thin form factor is one of the most challenging problems in display design today. The support for lens accommodation allows an observer to focus on virtual images that float at a distance to the physical device. This capability would allow for the correction of low-order visual aberrations, such as myopia and hyperopia.
Devices tailored to correct visual aberrations of human viewers have recently been introduced. Early approaches attempt to pre-sharpen a 2D image presented on a conventional screen with the inverse point spread function (PSF) of the viewer's eye. Although these methods slightly improve image sharpness, the problem itself is ill-posed. Fundamentally, the PSF of an eye with refractive errors is usually a low-pass filter—high image frequencies are irreversibly canceled out in the optical path from display to the retina. To overcome this limitation, the use of 4D light field displays with lenslet arrays or parallax barriers to correct visual aberrations was proposed by Pamplona et al. (PAMPLONA, V., OLIVEIRA, M., ALIAGA, D., AND RASKAR, R.2012. “Tailored displays to compensate for visual aberrations.” ACM Trans. Graph. (SIGGRAPH) 31.). For this application, the emitted light fields must provide sufficiently high angular resolution so that multiple light rays emitted by a single lenslet enter the same pupil (see FIG. 2). This approach can be interpreted as lifting the problem into a higher-dimensional (light field) space, where the inverse problem becomes well-posed.
Unfortunately, conventional light field displays as used by Pamplona et al. are subject to a spatio-angular resolution trade-off; that is, an increased angular resolution decreases the spatial resolution. Hence, the viewer sees a sharp image but at the expense of a significantly lower resolution than that of the screen. To mitigate this effect, Huang et al. (see, HUANG, F.-C., AND BARSKY, B. 2011. A framework for aberration compensated displays. Tech. Rep. UCB/EECS-2011-162, University of California, Berkeley, December; and HUANG, F.-C., LANMAN, D., BARSKY, B. A., AND RASKAR, R. 2012. Correcting for optical aberrations using multi layer displays. ACM Trans. Graph. (SiGGRAPH Asia) 31, 6, 185:1-185:12. proposed to use multilayer display designs together with prefiltering. Although this is a promising, high-resolution approach, the combination of prefiltering and these particular optical setups significantly reduces the contrast of the resulting image.
Pamplona et al. explore the resolution-limits of available hardware to build vision-correcting displays; Huang et al. [2011; 2012] show that computation can be used to overcome the resolution limits, but at the cost of decreased contrast. Accordingly it is desired to provide improve improved vision-correcting display solutions.